Playwright and author Calvin Alexander Ramsey appeared at the Boston Public Library on Sunday to talk about “Ruth and the Green Book,” a story about a young girl who takes a memorable car trip in the 1950s. Ramsey’s reading and discussion celebrated Black History Month. The writer, who was joined by BPL board member Mary Lentz and board chair Vivian Spiro, lives in Atlanta, but has spent plenty of time on Martha’s Vineyard.